In treat and produce (“TAP”) completions, multiple valves are installed at different layers of a wellbore adjacent a formation or hydrocarbon reservoir. A downhole dart is pumped down the TAP completion, past a first valve, and engages a valve ring of a second valve, which is located at the bottom of the wellbore, or at least nearer thereto than the first valve. When the downhole dart engages the valve ring of the second valve, the valve ring and the downhole dart form a seal. The pressure within the TAP completion can be increased to shift the second valve open when the seal is formed between the downhole dart and the valve ring. Once the second valve is opened, the formation adjacent the second valve can be fractured. In addition, the pressure in the TAP completion can compress or squeeze the valve ring of the first valve. The valve ring of the first valve then has a smaller inner diameter and can catch an additional downhole dart pumped into the TAP completion. This process can be repeated until each valve of the TAP completion is actuated and the formation adjacent the valves is fractured.
After the formation is fractured, the downhole darts typically have to be removed. Removal of the downhole darts, however, is problematic, because the valve rings usually all have about the same inner diameter, and the downhole darts usually have a common outer diameter. Accordingly, every downhole dart, except for the last one sent into the completion, is trapped between two valve rings. The downhole darts thus usually have to be dissolved or drilled out to allow the completion to be reopened. Dissolving darts, however, can limit the range of wellbore types and wellbore fluids that may be used in conjunction therewith, while drilling out the darts can be expensive and time-consuming.
A need exists, therefore, for a downhole dart that can engage a downhole valve assembly and can be efficiently recovered.